Oral contraceptives (OCs) are one of the most effective, safe and widely-used contraceptive methods available to women worldwide. The US differs from many other countries in that women still need a healthcare provider's prescription, often requiring an examination, to purchase OCs. Policy debate about the prescription requirement has focused on whether women could safely and effectively use oral contraceptives without mandatory contact with a healthcare provider. Specifically, questions remain as to whether women can screen themselves for contraindications;the degree to which the prescription requirement dissuades OC candidates from starting or continuing OC use;and whether written or other forms of information are an effective substitute or improvement on clinician contact. This interdisciplinary study will be fielded along the heavily traversed US-Mexico border separating Ciudad Juarez, Mexico and El Paso, Texas. The study setting provides a unique "natural experiment" environment in which to address these unanswered questions due to the fact that El Paso residents can, and frequently do, cross the border to purchase OCs in Mexican pharmacies, where prescriptions are not required. The first aim is to assess whether women are as capable of screening themselves for contraindications to OC use as health professionals. To this end, we will recruit a convenience sample of women from the general population in El Paso and make use of a simple checklist of contraindications as well as nurse's clinical assessment. Second, by comparing women recruited when they purchase OCs at pharmacies in Ciudad Juarez to controls recruited from family planning clinics in El Paso, the study will explore: women's motivations for buying OCs at each location, and the relation between procurement location and women's knowledge about OCs. Also, using a randomized controlled design, we will investigate the role of a simple written instruction leaflet about OCs in conveying information to women obtaining pills in Mexican pharmacies. Finally, a large prospective cohort of OC users recruited from Mexican pharmacies and the El Paso family planning clinics will be followed quarterly for nine months to assess whether their baseline decisions about OC procurement source are associated with satisfaction, compliance, continuation and unintended pregnancy. Our research will answer important questions regarding the appropriate role of medical supervision in OC provision and the factors influencing compliance and continuation. Additionally, it will add substantially to the slim literature on the increasingly important area of Hispanic fertility and contraceptive practice.